Generally, packing materials for use in packing and wrapping contents in a molten state are required to meet the following conditions, because packing forms influence packing materials.
(1) Contents to be packed may be sealed merely by application of heat or contact sealed by pressure.
(2) The surface of a resin layer covering packing materials may be melted by the heat of the contents to be packed and can adhere to the contents to prevent bacteria, mold or the like from penetrating and infecting the contents.
(3) Packing materials are provided with cold-resistant, oil-resistant and waterproofing properties.
(4) Packing materials may be cut easily by a knife or the like.
(5) Packing materials may be folded easily.
A method of packing and wrapping melted contents will be illustrated by taking processed cheese as an example.
Generally, among processed cheeses, a majority of carton-packed cheese of 150 to 400 grams for domestic use are packed and wrapped in a molten state. FIG. 1 shows a cheese package in which a piece of cheese, which was wrapped up tightly with a material (1) for packing, is packed in a carton consisting of a cardboard cover (2) and a receptacle (3). A method for packing a piece of cheese is illustrated in FIG. 2 in which a given amount of cheese, which was heated to about 75.degree. to 85.degree. C. and is in a molten state, is placed on the material (1) for packing. The material (1) is then folded within the carton cover (2). The unfolded portions of the material (1) are then folded so as to adhere to the molten mass of cheese, and the package of cheese is inserted into the receptacle (3). The carton which wrapped up the given amount of cheese is then pressed from the top and bottom, and from the right and left, to provide heat sealing and adhesion so that the packing is finished. Another mode of folding the material (1) for packing cheese around the carton cover (2) is shown in FIG. 3, where the side portions of the cheese packing material (1) are contact bonded together by means of a pressure sealer, as shown in FIG. 4, and then covered with a carton cover.
Since a molten mass of cheese is packed and wrapped in a manner as described above, the sealable layer of the cheese packing material need only be contact sealed or sealed by the heat of the mass of cheese to be packed, in order to be adequately sealed. The sealable layer of the cheese packing material is also required to possess a surface smooth enough for the molten mass of cheese to flow into every corner or end of the material folded around the cover. If a space were formed at a corner portion of the package, the air present therein would cause mold to grow. When a package of cheese is served, the packed cheese is usually cut by a knife without peeling off the packing material, so the material should be easy to cut with a knife.
Materials for packing sweet jelly of bean pastes in a molten state are mainly composed of paper, aluminum foil and polyethylene. FIG. 5 illustrates a tubular body formed by sealing together the side portions of a sheet of material, and then heat sealing the bottom portion thereof. A molten mass of sweetened bean paste at 80.degree. to 95.degree. C. is poured into the bottom-closed tubular body, and then the opening thereof is heat sealed in the same manner as the bottom portion.
This type of packing material contains aluminum foil so as to provide a prolonged preservation period of about one year. However, this manner of packing may allow an air pocket to be formed in the molten contents at the upper end of the package. Furthermore, this mode of heat sealing damages the shape of the top and bottom portions of the packed contents, impairing the commodity value. Packing materials containing aluminum foil do not allow the contents to be seen, so that the characteristic appearance of sweetened bean pastes, sweet jelly of Japanese chestnuts, adzuki bean pastes, and the like cannot be displayed.
Thus, the sealable layers of materials for packing contents such as cheese or sweetened bean pastes in a molten state are required to have different properties than sealable layers of packing materials for general use.